U.S.-backed forces in Syria have declared victory in the city of Raqqa, the self-proclaimed capital of the Islamic State. But four years of ISIS control and four months of fighting have left a majority of the city uninhabitable. Special correspondent Nick Schifrin reports on what this milestone means for Raqqa and what’s next for ISIS as it plans to revert to its roots and go back underground.

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Hari Sreenivasan:

Today in Syria, forces trained and supported by the United States declared victory in the city of Raqqa, the self-proclaimed capital of the Islamic State.

Beginning in June, Kurdish and Arab fighters had fought a brutal house-by-house battle, backed up by punishing airstrikes launched by the American-led coalition.

Now that the battle is over, what’s next for the war in Syria and for is?

Here’s special correspondent Nick Schifrin.

Nick Schifrin:

After four years of is, this is liberation. Kurdish fighters flashed V for victory in what was the heart of ISIS’ power.

But from above, after four months of fighting, Raqqa is ruined. In order to save the city, the U.S. destroyed it, says Times of London reporter Richard Spencer, who was in Raqqa this week.

Richard Spencer:

The whole city was completely empty. Every single house or apartment block or shop or industrial unit had been basically knocked to the ground by airstrikes. The coalition air forces went through the city building by building, and nothing is really left standing.

Nick Schifrin:

The U.S. dropped tens of thousands of pounds of bombs. The U.N. estimates 80 percent of the city is uninhabitable.

Hassan Hassan is a senior fellow at the Tahrir Institute for Middle East Policy.

Hassan Hassan:

They wanted basically to turn ISIS territories into a killing box. But that came at the expense of civilians. This is not what we expected the end would look like. We wanted this moment to be a moment of celebration.

Nick Schifrin:

For years, ISIS described control of territory the size of Portugal as proof of its power. Is collected taxes and released propaganda videos depicting moral police as neighborhood cops.

Now it has a plan to revert to its roots and go back underground, predicts former Deputy Assistant Secretary of Defense Andrew Exum.

Andrew Exum:

They’re not all going to go away, and we should be prepared for them to transition from having been a state-like entity into an insurgency, which, of course, is what they were before the declaration of the Islamic State.

Nick Schifrin:

ISIS doesn’t need land to use propaganda to spread ideology. It can continue to recruit online to launch terrorism, like the August van attack in Barcelona.

And in Syria, it’s down, but not out. The Syrian government is fighting ISIS in nearby Deir el-Zour. ISIS still controls 4,000 square miles in Syria and Iraq. And there’s no easy way to target its remaining 6,000 or so fighters. The group is wounded, but its wisdom has grown.

Hassan Hassan:

It has more experience in fighting and in kind of exploiting the political environment and the social division and so on and so forth. We have an environment that allows for groups like ISIS and others to arise and flourish and sustain themselves in these areas.

Nick Schifrin:

That’s because, in Syria, there’s no political solution in sight, no reconstruction or reconciliation or reform. Tens of thousands of Syrians fled their homes and are now living in camps.

Shia President Bashar al-Assad, backed by Russia and Iran, has made no concessions to his Sunni opponents.

Andrew Exum:

The Assad regime is not going to change its nature, and they’re going to continue to antagonize a Sunni Arab majority in Syria that could absolutely continue to create the conditions that would allow groups like Nusra or the Islamic State to arise or to come back.

Nick Schifrin:

ISIS has long exploited that political resentment. and so long as the resentment remains, ISIS will still have sympathizers.

But the U.S. priority is not fixing Syria. It’s exclusively defeating ISIS, which leads critics to argue the U.S. and its allies in Raqqa might have succeed tactically, but still have no strategy.

Hassan Hassan:

The problem is that there is always that short-term thinking that defines American foreign policy, especially not paying attention to the grievances and also the environment that led to the rise of groups like ISIS.

Nick Schifrin:

There’s no doubt this week marks a milestone. The square that once hosted ISIS beheadings hosted that Kurdish celebration.

The children ISIS recruited in Raqqa, their minds not old enough to resist propaganda, now safe in nearby shelters. And Raqqa’s women embraced their female liberators, and shed subjugation.

But there’s a lot of work left. And the very political and regional problems that helped launched this war still exist.

Nick Schifrin is a special correspondent at PBS NewsHour who has reported from more than 25 countries since moving overseas in 2007. For more than four years he covered breaking stories in South and Southwest Asia, from Benazir Bhutto's assassination in December, 2007, through a surge of violence in Kandahar, Afghanistan, in the spring of 2012.